Human diabetic autopsy eyes, fixed after minimal autolysis or unfixed, will be obtained through an eye donor program with the help of the local Eye Bank. We will then examine morphologically by light and electron microscopic techniques: (1) clinicopathologic correlations of the following surgical procedures performed in diabetic retinopathy: photocoagulation, vitrectomy, laser iridotomy, goniophotocoagulation; (2) structural changes of the blood-retinal barrier in retinal pigment epithelium, intraretinal blood vessels and preretinal neovascular proliferations; (3) presence and role of actin filament within retinal vascular pericytes and within fibrous preretinal membranes.